Four times a number decreased by twelve

Question

Write an algebraic expression for this verbal expression.

Answer 1

Four times a number decreased by twelve. "x" is my favorite variable so I will use it. I would interpret this to be 4(x-12).

 

4(x-12) is literally 4 times (a number "x" decreased by "-" 12).

 

If x were 22 then it would be 4(x-12) = 4(22-12) = 4(10) = 40

 

BUT some may read it as 4x-12 which would be 4(22)-12 = 88-12 = 76

 

So the reading of these two equations[4(x-12) and 4x-12] are very similar if not the same although they produce very different values for each number "x".

 

This highlights the importance of the order of operations (PEDMAS), interpretation, and clarity if ever asked to put an equation into words. 

Answer 2

It is important to look for key words in order to understand what operations are going on.

 

Lets look at the example:

 

Let n= a number (remember when it is says "a number" it is talking about a variable and a variable can be represented by any letter)

 

Four times a number decreased by twelve

4        x          n           -                12

 

times means multiplication
decreased means subtraction

 

answer: 4n-12

Answer 3

Let x = a number

 

 

The number is multiplied by four.  Then we subtract 12 from the product.

 

4x - 12